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Channel9 Session Downloader v1.93

NOTICE: The TechNet gallery will be retired in June, 2020. For future updates to these script, please visit my GitHub profile at https://github.com/michelderooij. Here you can also watch for updates, report bugs or ask questions, or contribute yourself. Official announcement

Microsoft didn't publish Ignite contents on Channel 9 (yet, if ever)
So, use this script which will download ppt/mp4s, scraping the ignite community portal
https://gallery.technet.microsoft.com/Ignite-2016-Slidedeck-and-296df316

Doesn't work for Technical Summit 2015 or Ignite 2016. It's failing to build the listbox for Categories and Speakers.
Looking at the Technical Summit 2015, neither the dc:creator or category properties are being utilized, so you're pulling back a nul result and it's dying when you try to load-listbox in line 629. One RSS entry populated the dc:creator, so that listbox only has a single item. Also your RSS url should probably be "http://s.ch9.ms/Events/microsoft-techncial-summit/Technical-Summit-2015-The-Next-Level/RSS/mp4high".
I think Ignite 2016 hasn't posted any files, yet.

Ignite2016 on-demand videos are put here https://myignite.microsoft.com/videos
Expect the downloadable videos and decks to be on ch9 at a later date/time.
That feed was down indeed - removed (not there anymore), added few others (eg AzureCon'15).